Versions
Succeeding the classic Visual Basic version 6.0, the first version of Visual Basic .NET debuted in 2002. As of 2014, seven versions of Visual Basic .NET are released.
2002 (VB 7.0)
The first version, Visual Basic .NET, relies on .NET Framework 1.0. The most important feature is managed code, which contrasts with the classic Visual Basic.
2003 (VB 7.1)
Visual Basic .NET 2003 was released with .NET Framework 1.1. New features included support for the .NET Compact Framework and a better VB upgrade wizard. Improvements were also made to the performance and reliability of .NET IDE (particularly the background compiler)
and runtime. In addition, Visual Basic .NET 2003 was available in the
Visual Studio.NET Academic Edition, distributed to a certain number of
scholars from each country without cost.
2005 (VB 8.0)
After Visual Basic .NET 2003, Microsoft dropped ".NET" from the name of the product, calling the next version Visual Basic 2005.
For this release, Microsoft added many features intended to reinforce Visual Basic .NET's focus as a rapid application development platform and further differentiate it from C#., including:
- Edit and Continue feature
- Design-time expression evaluation
- A pseudo-namespace called "My", which provides :
- Improved VB-to-VB.NET converter
- A "using" keyword, simplifying the use of objects that require the Dispose pattern to free resources
- Just My Code feature, which hides (steps over) boilerplate code written by the Visual Studio .NET IDE and system library code during debugging
- Data Source binding, easing database client/server development
To bridge the gaps between itself and other .NET languages, this version added:
- Generics
- Partial classes, a method of defining some parts of a class in one file and then adding more definitions later; particularly useful for integrating user code with auto-generated code
- Operator overloading and nullable types
- Support for unsigned integer data types commonly used in other languages
Visual Basic 2005 introduced the
IsNot operator that makes 'If X IsNot Y' equivalent to 'If Not X Is Y'. It gained notoriety when it was found to be the subject of a Microsoft patent application.2008 (VB 9.0)
Visual Basic 9.0 was released along with .NET Framework 3.5 on 19 November 2007.
For this release, Microsoft added many features, including:
- A true conditional operator, "If(condition as boolean, truepart, falsepart)", to replace the "IIf" function.
- Anonymous types
- Support for LINQ
- Lambda expressions
- XML Literals
- Type Inference
- Extension methods
2010 (VB 10.0)
In April 2010, Microsoft released Visual Basic 2010. Microsoft had planned to use Dynamic Language Runtime (DLR) for that release
but shifted to a co-evolution strategy between Visual Basic and sister
language C# to bring both languages into closer parity with one another.
Visual Basic's innate ability to interact dynamically with CLR and COM
objects has been enhanced to work with dynamic languages built on the
DLR such as IronPython and IronRuby.
The Visual Basic compiler was improved to infer line continuation in a
set of common contexts, in many cases removing the need for the "_" line
continuation character. Also, existing support of inline Functions was
complemented with support for inline Subs as well as multi-line versions
of both Sub and Function lambdas.
2012 (VB 11.0)
Visual Basic .NET 2012 was released along .NET Framework 4.5. Major features introduced in this version include:
- Asynchronous programming with "async" and "await" statements
- Iterators
- Call hierarchy
- Caller information
- "Global" keyword in "namespace" statements
2013 (VB 12.0)
Visual Basic 2013 was released .NET Framework 4.5.1 and Visual Studio 2013 but did not include new language features.
Comparison with the classic Visual Basic
Whether Visual Basic .NET should be considered as just another
version of Visual Basic or a completely different language is a topic of
debate. Apart from certain methods that have been moved and those that
can be automatically converted, the basic syntax of the language has not seen many changes that "break" compatibility. There are new additions to support new features, such as structured exception handling and short-circuited expressions. Also, two important data-type changes occurred with the move to VB.NET: compared to VB6, the
Integer data type has been doubled in length from 16 bits to 32 bits, and the Long data type
has been doubled in length from 32 bits to 64 bits. This is true for
all versions of VB.NET. A 16-bit integer in all versions of VB.NET is
now known as a Short. Similarly, the Windows Forms GUI editor is very similar in style and function to the Visual Basic form editor.
The version numbers used for the new Visual Basic (7, 7.1, 8, 9, ...)
clearly imply that it is viewed by Microsoft as still essentially the
same product as the old Visual Basic.
The things that have changed significantly are the semantics—from those of an object-based programming language running on a deterministic, reference-counted engine based on COM to a fully object-oriented language backed by the .NET Framework, which consists of a combination of the Common Language Runtime (a virtual machine using generational garbage collection and a just-in-time compilation engine) and a far larger class library.
The increased breadth of the latter is also a problem that VB
developers have to deal with when coming to the language, although this
is somewhat addressed by the My feature in Visual Studio 2005.
The changes have altered many underlying assumptions about the
"right" thing to do with respect to performance and maintainability.
Some functions and libraries no longer exist; others are available, but
not as efficient as the "native" .NET alternatives. Even if they
compile, most converted VB6 applications will require some level of refactoring to take full advantage
of the new language. Documentation is available to cover changes in the
syntax, debugging applications, deployment and terminology.
Comparative examples
The following simple examples compare VB and VB.NET syntax. Each example creates a "Hello, World" message box with an OK button.
VB6:
Private Sub Command1_Click() MsgBox "Hello, World" End Sub
VB.NET (MsgBox or MessageBox class can be used):
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click MessageBox.Show("Hello, World") End Sub
- Both Visual Basic 6 and Visual Basic .NET automatically generate the
SubandEnd Substatements when the corresponding button is clicked in design view. Visual Basic .NET will also generate the necessaryClassandEnd Classstatements. The developer need only add the statement to display the "Hello, World" message box. - All procedure calls must be made with parentheses in VB.NET, whereas
in VB6 there were different conventions for functions (parentheses
required) and subs (no parentheses allowed, unless called using the
keyword
Call). - The names
Command1andButton1are not obligatory. However, these are default names for a command button in VB6 and VB.NET respectively. - In VB.NET, the
Handleskeyword is used to make the subButton1_Clicka handler for theClickevent of the objectButton1. In VB6, event handler subs must have a specific name consisting of the object's name ("Command1"), an underscore ("_"), and the event's name ("Click", hence "Command1_Click"). - There is a function called
MsgBoxin theMicrosoft.VisualBasicnamespace which can be used similarly to the corresponding function in VB6. There is a controversy about which function to use as a best practice (not only restricted to showing message boxes but also regarding other features of theMicrosoft.VisualBasicnamespace). Some programmers prefer to do things "the .NET way", since the Framework classes have more features and are less language-specific. Others argue that using language-specific features makes code more readable (for example, usingint(C#) orInteger(VB.NET) instead ofSystem.Int32). - In VB 2008, the inclusion of
ByVal sender as Object, ByVal e as EventArgshas become optional.
The following example demonstrates a difference between VB6 and VB.NET. Both examples close the active window.
VB6:
Sub cmdClose_Click() Unload Me End Sub
VB.NET:
Sub btnClose_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnClose.Click Me.Close() End Sub
The 'cmd' prefix is replaced by the 'btn' prefix, conforming to the new convention previously mentioned.
Visual Basic 6 did not provide common operator shortcuts. The following are equivalent:
VB6:
Sub Timer1_Timer()
Me.Height = Me.Height - 1
End Sub
VB.NET:
Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick Me.Height -= 1 End Sub
Criticism
When first introduced, many long-time Visual Basic users complained
about Visual Basic .NET because initial versions dropped a large number
of language constructs and user interface features that were part of VB6
(which is no longer sold by Microsoft), and changed the semantics of
those that remained; for example, in VB.NET parameters are (by default)
passed by value, not by reference. Detractors refer pejoratively to
VB.NET as Visual Fred or DOTNOT.
One major complaint was that "edit-and-continue", the ability to fix
bugs by changing source code in a running program when it is paused at a
breakpoint and continue running the code, had been eliminated: this
feature was a major productivity aid that had attracted many developers
to VB6.
Many of the changes were necessary because they needed to reflect
differences between Windows Foundation Classes and equivalent classes in
the .NET framework (e.g., for user-interface controls): in addition,
certain changed features, such as restricting the scope of local
variables to the block where they were declared, and passing parameters
by value (which is the only means permitted in Java) make code less
error-prone. Reduced risk of error was also the justification for
removing features such as computed gosub/goto and the elimination of
line numbers (both a legacy of the BASIC language's FORTRAN heritage.)
In general, the idea was to make the .NET libraries, rather than
language-specific libraries, perform most of the work, so that code
written either in VB.NET or C# would compile to almost identical intermediate-code.
However, many of these semantic changes were not backward-compatible
with much existing code, and existing code required rewriting and
testing, a significant expense when the body of code was non-trivial in
size. As author Joel Spolsky
noted, "It was the first time a Microsoft upgrade did not respect the
work that users did using the previous version of a product."
Microsoft's IDE, Visual Studio, did support some degree of automatic
translation to VB.NET when VB6 code was pasted into Visual Studio. Also,
the VB.NET compiler reported multiple errors (up to a user-specified
threshold - e.g., 100 errors) all at once instead of one at a time, with
fixes to the source reducing the error list through a process of
background compilation. Despite this, adoption of VB.NET was still
delayed until 2005, when Microsoft finally reintroduced
edit-and-continue: this feature was also made available to C#
developers.
It is simpler to decompile languages that target Common Intermediate Language (CIL), including VB.NET, compared to languages that compile to machine code. Tools such as .NET Reflector can provide a close approximation to the original code due to the large amount of metadata provided in CIL. This is also true of early versions of Visual Basic (prior to VB5), which could not compile to native code.
Visual Basic 6.0 programs that are mainly algorithmic in nature can
be migrated with few difficulties, but certain types of code are more
troublesome, namely :
- Database support: .NET's framework for database access, ADO.NET, emphasizes disconnected operations, which use database-server resources as economically as possible by releasing them when not in use. This results in more scalable code than if the older Data Access Objects or ActiveX Data Objects were used, but the code is also more complex.
- Graphics: .NET has new (and more powerful) libraries for graphics.
- Unmanaged operations: .NET, like Java, emphasizes security, so unmanaged code is used only as a last resort.
Other syntactical differences relate to changes made to bring VB.NET
into alignment with other .NET languages, such as zero-based arrays (all
.NET arrays are only 0 to n-1 subscript, whereas classic VB arrays
could be defined as either zero-based or one-based (1 to n subscript)),
and structured exception handling (classic VB used a proprietary ON
ERROR mechanism); such changes can be difficult or impossible to convert
automatically, and converters typically flag such problem areas for
manual conversion.
In addition, the required runtime libraries for VB6 programs are provided with Windows 98 SE and above, while VB.NET programs require the installation of the significantly larger .NET Framework. The framework is included with Windows 7, Windows Vista, Windows XP Media Center Edition, Windows XP Tablet PC Edition, Windows Server 2008 and Windows Server 2003. For other supported operating systems such as Windows 2000 or Windows XP (Home or Professional Editions), it must be separately installed.
Microsoft's response to developer dissatisfaction focused around
making it easier to move new development and shift existing codebases
from VB6 to VB.NET. An offering in 2005 was the VBRun website, offering code samples and articles for:
- Using VB.NET to complete tasks that were common in VB6, like creating a print preview
- Integrating VB6 and VB.NET solutions (dubbed VB Fusion)
Cross-platform and open-source development
The creation of open-source tools for VB.NET development has been slow compared to C#, although the Mono development platform provides an implementation of VB.NET-specific libraries and a VB.NET 8.0 compatible compiler written in VB.NET, as well as standard framework libraries such as Windows Forms GUI library.
SharpDevelop and MonoDevelop are open-source alternative IDEs.
Examples
The following is a very simple VB.NET program, a version of the classic "Hello world" example created as a console application:
Module Module1 Sub Main() Console.WriteLine("Hello, world!") End Sub End Module
The effect is to write the text Hello, world! to the command line. Each line serves a specific purpose, as follows:
Module Module1
This is a module definition, a division of code similar to a class,
although modules can contain classes. Modules serve as containers of
code that can be referenced from other parts of a program.
It is common practice for a module and the code file, which contains it, to have the same name; however, this is not required, as a single code file may contain more than one module and/or class definition.
It is common practice for a module and the code file, which contains it, to have the same name; however, this is not required, as a single code file may contain more than one module and/or class definition.
Sub Main()
This is the entry point where the program begins execution. Sub is an abbreviation of "subroutine."
Console.WriteLine("Hello, world!")
This line performs the actual task of writing the output. Console is a system object, representing a command-line interface and granting programmatic access to the operating system's standard streams. The program calls the Console method WriteLine, which causes the string passed to it to be displayed on the console. Another common method is using MsgBox (a Message Box).
This piece of code is a solution to Floyd's Triangle:
Imports System.Console Module Program Sub Main() Dim rows As Integer ' Input validation. Do Until Integer.TryParse(ReadLine("Enter a value for how many rows to be displayed: "), rows) AndAlso rows >= 1 WriteLine("Allowed range is 1 and {0}", Integer.MaxValue) Loop ' Output of Floyd's Triangle Dim current = 1 For row = 1 To rows For column = 1 To row Write("{0,-2} ", current) current += 1 Next WriteLine() Next End Sub ''' <summary> ''' Shadows Console.ReadLine with a version which takes a prompt string. ''' </summary> Function ReadLine(Optional prompt As String = Nothing) As String If prompt IsNot Nothing Then Write(prompt) End If Return Console.ReadLine() End Function End Module
Source : http://www.wikipedia.com
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